QoB: A QoB driver job can fail because a HailContext already exists #15072
Description
Reported in https://hail.zulipchat.com/#narrow/channel/223457-Hail-Batch-support/topic/Error.20in.20QoB/with/539119133. Potential fixes discussed in https://hail.zulipchat.com/#narrow/channel/300487-Hail-Batch-Dev/topic/QoB.20JVM.20Job/with/539119265.
This bug appears to have been introduced by #14698. Before that, the driver job used this logic to ensure a HailContext was created:
if (HailContext.isInitialized) {
HailContext.get.backend = backend
log.info("Default references added to already initialized HailContexet.")
} else {
HailContext(backend, 50, 3)
log.info("HailContexet initialized.")
}
This was changed to unconditionally attempt to create a HailContext.